Variable geometry marine propulsor

ABSTRACT

A marine propulsive apparatus and a device and method for increasing the apparatus&#39;&#39; efficiency by controlling the amount of wetting of the apparatus over a range of speeds. A housing, mounted in a cavity formed in the stern of a ship, encloses a drive shaft connected to a propeller. A control surface is pivotally connected to the hull of the ship ahead of the propeller and in a raised position contacts the stern portion of the hull to form the upper wall of the cavity. A hydraulic device is used to raise and lower the control surface, the latter directing the flow of water across the propulsive apparatus. As the speed of the ship increases wetting of the propulsive apparatus is decreased.

United States Patent 1 Mantle Aug. 20, 1974 VARIABLE GEOMETRY MARINEPROPULSOR [75] inventor: Peter J. Mantle, Tacoma, Wash.

[22] Filed: May 24, 1973 [21] Appl. No.: 363,447

' [52] US. Cl 115/34 R, 114/66.5 P

[51] Int. Cl B63h 5/06. [58] Field of Search 115/34, 39, 41 R, 14;

[56] References Cited UNITED STATES PATENTS 130,110 8/1872 Dodge 115/41R 2,135,907 ll/1938 Miller 115/41 R 2,265,079 12/1941 Mettair 115/41 R2,377,442 6/1945 Osterhoudt.... 114/235 2,928,365 3/1960 Moon 114/66.5 P2,929,346 3/1960 Perce ll4/66.5 P

Carter, Jr. 114/665 P Shields 115/14 Primary Examiner-Robert G. SheridanAssistant Examiner-Donald W. Underwood Attorney, Agent, or Firm-R. S.Sciascia; P. Schneider; R. B. Rothman [57] ABSTRACT A marine propulsiveapparatus and a device and method for increasing the apparatusefficiency by controlling the amount of wetting of the apparatus over arange of speeds. A housing, mounted in a cavity formed in the stern of aship, encloses a drive shaft connected to a propeller. A control surfaceis pivotally connected to the hull of the ship ahead of the propellerand in a raised position contacts the stern portion of the hull to formthe upper wall of the cavity. A hydraulic device is used to raise andlower the control surface, the latter directing the flow of water acrossthe propulsive apparatus. As the speed of the ship increases wetting ofthe propulsive apparatus is decreased.

7 Claims, 4 Drawing Figures VARIABLE GEOMETRY MARINE PROPULSORBACKGROUND OF THE INVENTION The present invention relates generally tomarine propulsion devices and more particularly to a method andapparatus for increasing the efficiency of a propulsion device.

Top speeds of high-speed, marine craft have heretofore been limited bythe drag of the propulsion appendages required to support the propeller.Partially submerged propellers are not capable along of solving thisproblem, because such propellers lack thrust at low speeds. Low speedsrequire more submergence to absorb the thrust and torque of thepropeller and maintain maximum efficiency. The problem is intensified oncraft required to operate at both low and high speeds at high thrustlevels, as for example, air cushion vehicles and surface effect shipswhich have high hump drag and high design speed drag.

Variable geometry hulls employed in the past have not been addressed tothis problem, since the speed of large marine craft until relativelyrecently did not necessitate its solution. Propulsion devices in thepast have actually varied hull geometry, generally to ensure completewetting of the propeller.

SUMMARY OF THE INVENTION The present invention recognizes that at highspeeds the propulsive force, thrust less drag,-of apropulsion system isseverely affected by the drag of the submerged propeller and appendagesrequired to support the propeller. The invention solves this problem byprovidings system which controls wetting of both the propeller and itssupport structure as the speed of the craft varies.

OBJECTS OF THE INVENTION An object of the present invention is tooptimize the efficiency of a propulsion system over the entire speedrange of a ship.

Another object is to control the wetting of a propeller and itssupporting structure as the speed of 'a ship var- 1es.

A further object is to provide fully submerged propeller performance athigh speed.

Obviously many modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic of the sternposition of a hull section partially in cross section illustrating thevariable geometry marine propulsor in raised position;

FIG. 2 is a view of the rear of a preferred hull incorporating thepresent invention;

FIG. 3 is a schematic similar to FIG. 1 showing the control surface inits fully lowered position; and

FIG. 4 is another view of the rear of a preferred hull incorporating thepresent invention with the control surface in the lowered position.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1, which illustrates apreferred embodiment of the variable geometry propulsor, shows apropeller 2 mounted on a housing 4 which is connected to the sternportion 8 of the hull of a ship. The housing 4 encloses drive shafts(not shown) which are connected to the propeller and serves as apropeller mounting. A control surface 10 is pivotally connected at 12 tothe hull ahead of the propeller. The pivotal connection may be madeusing any suitable hinge.

A hydraulic actuator 16, of any suitable type, is connected via shaft 18to appendage I4. Appendage 14 is rigidly affixed to control surface 10by, for example, welding. The actuator deploys the control surface inselected positions depending on the speed of the ship. At low speeds,for example Froude Number less than 1.0, a fully submerged propellerwith percent disc wetting provides the maximum propulsion force. At highspeeds,,Froude Number greater than 1.0, the advantage of 100 percentdisc wetting is lost by the drag of the housing structure 4 or otherappendages (not shown) required to support the propeller. At low speedthe control surface 10 is in the raised position as shown in FIG. 1 andthe water level just behind the hull 8 is indicated by the numeral 6.

FIG. 2 is a view of the rear of a preferred hull incorporating thepropulsor. As can be seen in FIG. 2, the housing 4 is within a cavity inthe stern portion of the hull. The cavity is in the form of a triangularprism. The disc 20 illustrates the area covered by propeller 2. Theinterior of the disc 20 is completely filled with dotted lines toindicate that when the control surface is in the raised position asshown in FIG. 2, 100 percent of propeller 2 and housing 4 is submerged.

FIGS. 3 and 4, in which like numerals indicate like structure, depictthe control surface 10 in its lowered position. As can be seen in theFigures, at least 50 percent of the propeller and housing 4 are nolonger submerged. This control surface position is used for running athigh speeds. One can also see that the propeller 2 in the preferredembodiment is just outside the cavity formed in the stern portion of thehull 8. In addition, the upper face of control surface 10 is shapedcomplementary with respect to the hull surface that forms the upper wallof the cavity. In the raised position of the control surface 10,therefore, its upper face smoothly overlaps and contacts the hull 8.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is therefore to beunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

I claim:

1. A ship comprising:

a hull having a stern portion, said stern portion having a cavitytherein, said cavity being formed between depending sides of the hull atthe stern portion of the hull;

a housing rigidly affixed to said stern portion and depending into saidcavity, said housing being immovable with respect to said hull;

a drive shaft within said housing, immovable vertically and horizontallywith respect to said hull;

a propeller connected to said drive shaft;

control surface means pivotally mounted on said hull within the cavityahead of said propeller for directing the flow of water over saidpropeller to change the degree of submergence of the propeller without asubstantial change in position or attitude of the hull relative to thewater surface; and

raised position.

4. The ship of claim 3 wherein the propeller is outside the cavityformed in the stern portion of said hull.

5. The ship of claim 3 wherein the upper face of said control surface isflat.

6. The ship of claim 5 wherein the cavity formed in said stem is in theshape of a triangular prism.

7. The ship of claim 6 wherein the propeller is outside the cavityformed in the stern portion of said hull.

1. A ship comprising: a hull having a stern portion, said stern portionhaving a cavity therein, said cavity being formed between dependingsides of the hull at the stern portion of the hull; a housing rigidlyaffixed to said stern portion and depending into said cavity, saidhousing being immovable with respect to said hull; a drive shaft withinsaid housing, immovable vertically and horizontally with respect to saidhull; a propeller connected to said drive shaft; control surface meanspivotally mounted on said hull within the cavity ahead of said propellerfor directing the flow of water over said propeller to change the degreeof submergence of the propeller without a substantial change in positionor attitude of the hull relative to the water surface; and deploymentmeans for moving said control surface means into and out of contact withthe stern portion of said hull.
 2. The ship of claim 1 wherein saidcOntrol surface means comprises a control surface whose bottom face isplanar.
 3. The ship of claim 2 wherein the control surface has an upperface contacting the stern portion of said hull when said control surfaceis in a raised position, said upper face being shaped complementary tosaid stern portion to fit smoothly against said stern portion in saidraised position.
 4. The ship of claim 3 wherein the propeller is outsidethe cavity formed in the stern portion of said hull.
 5. The ship ofclaim 3 wherein the upper face of said control surface is flat.
 6. Theship of claim 5 wherein the cavity formed in said stern is in the shapeof a triangular prism.
 7. The ship of claim 6 wherein the propeller isoutside the cavity formed in the stern portion of said hull.